cracked exhaust manifold?

["mcji6gr2@stud.umist.ac.uk" <mcji6gr2@stud.umist.ac.uk>]

Bought an 86, D reg 80 sport. I'm really pleased with it so far:- full 
audi service history, 1 owner from new, mint body work etc...I have 
a few questions though and wonder if someone will know:

There was a strange ticking when the engines underload at any 
rpm. sounded to me like piston slap but according to my mechanic 
the bottom end will be fine and listening to it for a couple of 
seconds not even underload and said it's a crackedd exhaust 
manifold. what do u think? The cars done 141k genuine mileage 
and u  can see a v. small amount of blue smoke if u watch from 
behind in 1st gear at high rpm
Do u know if it's galvanised - absolutely no rust - it's an 86 series 1 
model.
I'm a very new member to the list so sorry to be "taking rather than 
giving"!
Hope someone can help!

cheers

Guy